Assuming you are referring to a commit made via a working copy:
1. Open the working copy window.
2. Open the working copy’s repository window.
3. Drag the revision that you wish to revert from the log list into the working copy window.
4. A merge sheet should appear on the WC window. (It should be set to `single change` & `reverse merge`.)
5. Click Dry Run. If the output appears correct then you can choose to click OK to actually perform the merge.
OK?
CHRIS